Method of and apparatus for forming a plastic lined tunnel

ABSTRACT

A method of forming a plastic lined tunnel including:  
     positioning a tube section of plastics material in a tunnel portion to be lined;  
     positioning a removable wall portion of an internal form assembly in the tube section to provide a temporary base wall wherein the internal form assembly further includes a collapsible wall portion;  
     engaging the base wall with at least one wall of the tunnel to retain the tube section in position;  
     transporting the collapsible wall portion along the temporary base wall into position for engagement with the temporary base wall within the tube section;  
     erecting the internal form assembly into an operative condition within the tube section as to conform the tube section to its desired shape;  
     introducing grout between the outer surface of the tube section and the tunnel wall so as to substantially fill the void therebetween and to retain the tube section in position;  
     collapsing the internal form assembly and removing the internal form assembly from the lined tunnel portion.

FIELD OF THE INVENTION

[0001] This invention relates to a method of and apparatus for forming aplastic lined tunnel.

BACKGROUND OF THE INVENTION

[0002] Typically, drains and tunnels are lined with plastic to providecorrosion resistance and a smooth internal bore so as to minimisepumping losses.

[0003] For large diameter drains and tunnels, the plastic liner istypically made by spiral winding ribbed plastic strip onto itself so asto form a spiral wound tube, the strip edges being formed so as toeither engage complementary edge portions or to join the edges with ajoining strip. The plastic strip may be forced into a spiralconfiguration inside an internal forming means such as illustrated inAustralian Patent No. 530251 or it may be wound about a mandrel of thedesired diameter such as is illustrated in U.S. Pat. No. 3,606,670.

[0004] Mostly, such plastic linings are utilised for repair of olddrains and tunnels and thus it has also been proposed to form the linerdirectly into the tunnel being repaired so that the liner is advancedthrough the tunnel as the liner is formed. Such an arrangement is shownin Australian Patent No. 57422/98.

BRIEF SUMMARY OF THE INVENTION

[0005] We have now found a method of and apparatus for forming a plasticlined tunnel which will be efficient and reliable in use.

[0006] According to one aspect of the present invention there isprovided a method of forming a plastic lined tunnel including:

[0007] positioning a tube section of plastics material in a tunnelportion to be lined;

[0008] positioning a removable wall portion of an internal form assemblyin the tube section to provide a temporary base wall wherein theinternal form assembly further includes a collapsible wall portion;

[0009] engaging the base wall with at least one wall of the tunnel toretain the tube section in position;

[0010] transporting the collapsible wall portion along the temporarybase wall into position for engagement with the temporary base wallwithin the tube section;

[0011] erecting the internal form assembly into an operative conditionwithin the tube section as to conform the tube section to its desiredshape;

[0012] introducing grout between the outer surface of the tube sectionand the tunnel wall so as to substantially fill the void therebetweenand to retain the tube section in position;

[0013] collapsing the internal form assembly and removing the internalform assembly from the lined tunnel portion.

[0014] Suitably the tube section may be formed of any plastics materialwhich can provide the chemical and physical properties to ensuresufficient corrosion resistance and toughness necessary for theapplication. When the application requires minimized pumping losses, thetube section is formed with a smooth internal surface and a keyed outersurface for improving the bond between the tube section and the grout.In one embodiment the keyed outer surface may simply be a grooving orroughness on that surface. Alternatively the outer surface may have oneor more key members thereon for interlocking the tube into the groutplaced between the tube section and the tunnel wall.

[0015] A suitable tube section may be formed with a series of encirclingflanged ribs about its outer surface for interlocking the tube into agrout placed between the tube section and the tunnel wall. Alternativelyit may be formed with a plurality of individual projections tabs or tiesabout its outer surface for interlocking the tube into a grout.

[0016] Preferably the tube section is a spiral wound tube produced froma strip of plastics material having T-shaped ribs extending about itsexternal surface. Suitably the spiral joint between edges of the stripfrom which the tube is formed is welded, either internally or externallyand preferably internally in a groove formed between the mating edges ofthe strip. It is also preferred that the strip interlocks along matingedges and each interlocking formation has an external return rib forinterlocking with the grout.

[0017] The tube section may be prefabricated and transported to the openend of the tunnel. Alternatively bales of plastic strip which can beformed into the tube sections may be transported to a fabrication unitadjacent the open end of the tunnel where the tube section may befabricated. Suitably the tube section is introduced from one end of thetunnel and positioned within the tunnel remote from that one end.Subsequent tube sections may be introduced and positioned in abutmentwith the preceding tube section and the internal form assembly may bemoved progressively from tube section to tube section toward that oneend. The tube section may be positioned in the tunnel portion by anyconvenient means such as by a rail mounted tube carrier where the railsare located temporarily or permanently fixed to the tunnel. The tubecarrier may have forks suitable for carrying the tube section, whichforks permit fine control over the position and orientation of the tubesection to facilitate placement of the tube section within the tunnelportion.

[0018] Abutting tube sections may be joined to one another by anyconvenient means such as by being adhered, taped or overlapped andmechanically fastened. Most suitably the tube sections are joined to oneanother by a welding process.

[0019] The exposed end of tube section forming a liner may be providedwith locating means such as an external collar to form a socket intowhich the introduced end of the next tube section may spigot so as toalign the abutting tube sections.

[0020] The collar may be continuous or gapped or otherwise formed so asto allow grout to extend into the void between the collar and the keyedouter surface of tube sections formed with interlocking means.

[0021] The internal form assembly suitably may comprise a series ofsegments including upper segments pivotally connected to one another asthe collapsible wall portion which is engageable with a temporary basewall, composed of a segment or segments. The collapsible wall portionmay be carried on a carriage which may move along the base wall.

[0022] Suitably such a carriage may include transport means whichextends beyond a tube section for transporting a base wall segment frombeyond one end of a tube section to beyond the other end of the tubesection for shifting the base wall segment or segments from a previouslylined tunnel portion, through an adjacent lined section into a tubesection introduced into an unlined tunnel portion.

[0023] Suitably the base wall is formed in segments which may be liftedfrom one longitudinal edge or for rotation to an upstanding attitude soas to lie alongside the carriage for transport therepast.

[0024] The base wall may be engaged with at least one wall of the tunnelby a locating means which extends beyond the ends of the tube section orthrough supports extending through the tube section. Suitably the formof the tube section is cylindrical and the base wall is locatedsubstantially coaxially with the tunnel.

[0025] The internal form assembly may be erected into an operativecondition to conform the tube section to the desired shape by anyconvenient means. Where the collapsible wall portion comprises hingedsegments, the end segments may be engaged with the base wall and thecollapsible wall portion erected by urging the remaining segments intoengagement with the remainder of the tube section. The ends of segmentsmay be shaped such that once erected the segments hold themselves in thedesired shapes. These segments may take the form of overcentre tabs forease of erection and collapse.

[0026] The grout may be introduced into the space between the outersurface of the tube section and the tunnel wall in any suitable mannerso as to substantially fill the void therebetween and to retain the tubesection in position. Suitably the grout is concrete which is pumped intoposition from a supply tube extending along the top outer surface of thetube sections. The hose may have a concertina or other retractablesupport in the tunnel to which it is retracted after filling the voidwhich may extend about a plurality of tube sections.

[0027] The internal form assembly may be collapse by any convenientmeans and will generally follow the reverse process to the erection ofthe internal form assembly.

[0028] In a preferred embodiment there is provided a continuous methodfor forming a plastics lined tunnel whereby the internal form assemblyis moved into an adjoining portion of the tunnel into which a tubesection has been positioned so as to progressively form a continuousplastic lined tunnel.

[0029] In another aspect this invention resides broadly in a ribbedplastic strip for forming spiral wound tubing having complementary edgeformations which engage to form the spiral wound tube and each edgeformation having an projection adapted for interlocking engagement withsurrounding grout so as to hold the tube section in position againstexternal pressure such as ground water pressure. Suitably the projectionis a continuous laterally projecting rib extending from the edgeformation spaced from the liner wall. Suitably the edge formationsengage so as to form an external groove between the joined edgeformations into which bonding material may be placed to bond the stripstogether. Preferably the bonding material is deposited by welding.

[0030] In yet a further aspect, this invention resides broadly in amethod of forming a mandrel formed spiral wound pipe, including:

[0031] spiral winding plastic strip onto a mandrel;

[0032] joining together the adjacent edges of the strip to form a tube;

[0033] ejecting a fluid from the mandrel beneath the formed tube to freethe formed tube from the mandrel, and

[0034] sliding the formed tube from the mandrel.

[0035] Suitably the edges of the spiral wound strip are joined togetherby welding. The edges may also be joined through complementary edgeformations or joined with a joining strip. Preferably the spiral woundstrip is a ribbed plastic strip made in accordance with an aspect ofthis invention as defined above and most suitably the joining weld isdeposited in the external groove formed between joined edges.

[0036] In order that this invention may be more readily understood andput into practical effect, reference will now be made to theaccompanying drawings which illustrate a preferred embodiment of theinvention, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 is a side view of the mandrel assembly with a plastic tubepart formed thereon;

[0038]FIG. 2 is a cross-sectional plan view of the mandrel assemblyillustrated in FIG. 1;

[0039]FIG. 3 is an end view of the tube forming assembly showing themandrel and its associated strip feed mechanism;

[0040]FIG. 4 is a cross-sectional side view showing the installation ofthe plastic lining in a tunnel;

[0041]FIG. 5 is a corresponding view illustrating the relocation ofportion of the internal former for the plastic lining;

[0042]FIGS. 6, 7 and 8 are a series of views illustrating the relocationof the internal former for the lining;

[0043]FIG. 9 illustrates the arrangement for feeding concrete to theannular space between the liner and the tunnel;

[0044]FIG. 10 is an end view of the preferred form of plastic strip usedto form the tube section;

[0045]FIG. 11 illustrates the junction between complementary edgeportions of the strip of FIG. 10;

[0046]FIG. 12 is an end view illustrating the formation of a joiningweld between tube sections installed in the tunnel;

[0047]FIG. 13 illustrates a method of post filling voids created afterinitial grouting, and;

[0048]FIG. 14 illustrates a typical method of aligning one tube sectionwith the next during installation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0049] According to this embodiment the tunnel is lined to providesmooth plastic lined bore. Since large diameter thin walled plasticpipes or tubes are difficult to handle and transport, the lining tubesections are formed on site as illustrated in FIGS. 1 to 3 utilisingextruded plastic strip as illustrated in FIGS. 10 and 11.

[0050] For this purpose lengths of the plastic extrusion 10 is deliveredin the form of wound and strapped bales 11, each sufficient to form oneliner 12 when wound helically. Each bale 11 is loaded onto a spool 13 ona travelling frame 14 positioned at the outer end of the forming mandrel15.

[0051] The free end of the extrusion 10 is fed through a strip guide,under a bend roller 17 and a nip roller 18 and then clamped into a startend clamp 19. The mandrel 15 will then be rotated slowly, driven by avariable speed hydraulic drive 20, drawing the strip 10 off the bale 11and onto the mandrel 15.

[0052] The purpose of the strip 10 guide is to control the helix angleat which the strip 10 is wound onto the mandrel. The bend roller 17applies a radial force to the strip 10 to bring it into contact with theouter skin of the mandrel and the nip roller 18 pushes the complementaryedges 22 and 23 of adjacent strips into engagement so that the innerfaces of the coiled strip 10 lie on the mandrel 15.

[0053] When one full turn of the mandrel 15 has been completed a plasticextrusion welder 24 is started to form a weld bead into the formedV-shaped spiral recess 25 formed continuously along the outside of thejoined edges 22 and 23.

[0054] Several driving rollers 26 bear on the leading edge 27 of theformed portion of the tube section 30 and drive the rail mountedtravelling frame 14 on which the bale 11 is rotatably mounted foradvancement as the tube section 30 is formed.

[0055] When the tube section 30 is fully wound and welded each end ofthe tube section 30 is trimmed square to the axis of the mandrel 15. Thestart end clamp 19 is then released and low pressure air is injectedinto a plenum 28 formed between inner and outer skins 29 and 29′ of themandrel. The air escapes from the mandrel through apertures in the outerskin 29 causing the formed plastic tube section 30 to swell slightly sothat it is easily removed from the mandrel 15.

[0056] A cradle is positioned at one end of the mandrel 15 so that asthe completed tube section 30 is slid from the mandrel it is seated in arespective cradle. Suitably there are three cradles along the length ofthe tube section 30 on rails which will allow the tube section 30 to bemoved clear of the mandrel 15.

[0057] To maintain the tube sections 30 in the form of the liners 12required, when each tube section 30 is slid from the mandrel 15 a seriesof supporting spiders 32 is installed in the tube sections 30, eachbeing aligned with a cradle. A crane with a spreader bar and straps willlift each tube section 30 to a storage yard.

[0058] The formed tube sections 30 are inspected to ensure that they arefree of dirt or any other foreign material and then each is craned tothe collar of the shaft using a spreader bar and straps for installationas a liner 12. Each tube sections 30 is lowered into the tunnel 40 untilit is positioned over the top of the tunnel rails 36 and aligned with atube carrier 37 thereon.

[0059] In this embodiment, each tube section 30 is suitably 9 meter longand is transported through the tunnel 40 to its installation point onthe rail mounted tube carrier 37. The tube carrier 37 will carry eachtube sections 30 on cantilevered forks 42 through the tunnel 40 forpositioning adjacent the previously installed liner 12. Suitably theforks 42 is able to slew left to right, cross travel, raise and lowerand articulate upwards and downward to enable each liner 12 to bealigned and correctly mated to the previously installed tube section 30.

[0060] Each tube section 30 is supported internally with spiders 32 toprevent it buckling while it is being transported and positioned in thetunnel 40. The leading edge of the tube section 30 is protected bybuffers temporarily installed thereon to protect the tube section 30from touching any part of the excavation on its journey through thetunnel 40.

[0061] The tube section 30 will then be spigoted into the socket 43formed about the end of the previously installed liner 12, asillustrated in FIG. 14 to provide quick and accurate coaxial alignmentof the tube sections 30 so as to form a continuous liner 12 through thetunnel 40. The socket is suitably provided with apertures therethroughso as to prevent formation of voids about the installed liner.

[0062] The tube sections 30 are welded at their junction once theconcrete has been placed and the internal form assembly 38 removed.Welding is carried out using a rotating welding arm 44 fitted withextrusion welders set at the appropriate radius or biased to the desiredproximal position to effect the weld.

[0063] As illustrated in FIGS. 6 to 8, the internal form assembly 38consists of three base wall panels 39 and a collapsible obvert formassembly 46 which cooperate to provide a cylindrical outer wall when intheir interlocked operative position. The obvert form assembly 46 may becollapsed by folding at the pivot joints 55 between its panel sectionsand lifted free from the base wall panels 39 by a mobile form carrier 47supported on the base wall panels 39.

[0064] After the tube section 30 has been positioned to form a liner 12,the remote one of the three base wall panels 39 is lifted by an elevatedrail 56 of the form carrier, tilted about 90° to the positionillustrated in FIG. 6 and then transported to the opposite end of therail 56 where it is lowered into position in the base of the newlyinstalled tube section 30, see FIG. 5.

[0065] Two spud bar holes 57 are then formed through the liner 12 usingthe holes in the invert form segment as a template, to allow the spudbars to locate the invert form and liner 12 to supporting segments 58installed during excavation.

[0066] This process is repeated until all base wall panels 39 have beenrelocated to allow the form carrier 47 to travel thereacross carryingthe collapsed obvert form assembly 46 into the next tube section 30 tobe installed where it is extended to cooperate with the base wall panels39 to hold the tube section 30 in its designed shape during theconcreting operation. As the obvert form assembly 46 and carrier 47 moveforward the tube carrier 37 will retreat and the support spiders 32 willbe removed and the tube carrier 37 will be transported out to receiveanother liner.

[0067] Upon installation of the internal form assembly 38 the liner 12is made rigid whereafter the side and top of the liner 12 is spudded tothe excavation so that it is held in its design position whileconcreting. Typically six spuds will be used around the circumference ofthe liner 12 every three linear meters.

[0068] As the tube carrier 37 and its locomotive 60 return for anotherliner 12 the concrete hands will prepare for the next tube sectioninstallation by removing the next 9 meters of excavation rail track 36and washing down the walls.

[0069] A slick line 62 for concrete delivery is installed along thelength of the pour in the tunnel crown. It is held in place by brackets63 each with a roller assembly 64 to enable the slick line 62 to moveeasily. See FIG. 9.

[0070] Concrete is delivered to a concrete pump 65 on the surface andpumped down a drophole 66. Suitably a plurality of dropholes are formedabout 300 m apart on the surface along the tunnel 40. The distancebetween dropholes may vary, depending on surface infrastructure and/orliner 12 installation requirements and the like.

[0071] The slick line 62 underground is supported in a folded manner ona rail mounted scissors type support onto which the slick line isgathered as the pour progressively fills the cavity between the tubesections 30 and the tunnel wall. This arrangement has the advantage thatit allows a continuous pour for the full length of each installed liner.

[0072] Suitably the concrete to be used for the backfill of the tunnelliners will be low shrink, flowable, self compacting, high strength (40Mpa) and have a low water/cement ratio. Such a mix design will allowease of placement, structural integrity and reduce backfill/proof groutto a minimum.

[0073] During installation, spud bar holes are drilled through the liner12 to extend into the surrounding tunnel wall. This may create voids inthe finished concrete grout. These are filled through a grout pipe 70 asillustrated in FIG. 13. The pipe 70 provided with internal airbleed/tell tale tube 71 is placed in the spud bar hole and held in placewith a thrust leg 72. The air bleed tube 71 is extended to within 20 mmof the top of the hole and as grout is pumped into the void air isexpelled through the air bleed tube 71 until the void has been filled,whereupon grout will appear from the tube 71. Grouting at each hole maybe repeated to ensure that there has been no grout leakage and any voidshave been successfully filled. When routing has been completed, theholes in the liner 12 are capped and welded. On completion of all thewelding, spark testing of the completed tunnel 40 will occur.

[0074] The formed lined tunnel will have a smooth cylindrical internalsurface with a 2400 mm inside diameter and a liner wall thickness notless than 3 mm. The liner will be watertight from both the inside andoutside and able to withstand an external hydrostatic pressure whengrouted/concreted into the tunnel 40.

[0075] It will be seen from FIGS. 10 and 11 that the strip 10 has aseries of equally spaced T shaped ribs 75 formed integrally on its outersurface which interlock with the concrete grout to resist the externalhydrostatic pressures which may be applied in use.

[0076] Furthermore the complementary edge formations 22 and 23 are soformed that each has a return flange 77 and 78 formed integrallytherewith so that the joined edges also interlock with the grout toensure that the liner has equal resistance to external pressuresthroughout its length.

1. A method of forming a plastic lined tunnel comprising: positioning atube section of plastics material in a tunnel portion to be lined;positioning a removable wall portion of an internal form assembly in thetube section to provide a temporary base wall wherein the internal formassembly further includes a collapsible wall portion; engaging the basewall with at least one wall of the tunnel to retain the tube section inposition; transporting the collapsible wall portion along the temporarybase wall into position for engagement with the temporary base wallwithin the tube section; erecting the internal form assembly into anoperative condition within the tube section as to conform the tubesection to its desired shape; introducing grout between the outersurface of the tube section and the tunnel wall so as to substantiallyfill the void therebetween and to retain the tube section in position;collapsing the internal form assembly and removing the internal formassembly from the lined tunnel portion.
 2. A method according to claim 1wherein the tube section is formed with a smooth internal surface and akeyed outer surface for improving the bond between the tube section andthe grout.
 3. A method according to claim 1 wherein the tube section isa spiral wound tube produced from a strip of plastics material havingT-shaped ribs extending about its external surface.
 4. A methodaccording to claim 1 wherein tube section forming a liner may beprovided with locating means such as an external collar to form a socketinto which the introduced end of the next tube section may spigot so asto align the abutting tube sections.
 5. A method according to claim 1wherein the internal form assembly suitably comprise a series ofsegments including upper segments pivotally connected to one another asthe collapsible wall portion which is engageable with a temporary basewall, composed of a segment or segments.
 6. A method according to claim1 wherein the collapsible wall portion may be carried on a carriagewhich may move along the base wall.
 7. A method according to claim 6wherein the carriage includes transport means which extends beyond atube section for transporting a base wall segment from beyond one end ofa tube section to beyond the other end of the tube section for shiftingthe base wall segment or segments from a previously lined tunnelportion, through an adjacent lined section into a tube sectionintroduced into an unlined tunnel portion.
 8. A method according toclaim 1 wherein the base wall is engaged with at least one wall of thetunnel by a locating means which extends beyond the ends of the tubesection or through supports extending through the tube section.
 9. Amethod according to claim 1 wherein the grout is cement.
 10. A methodaccording to claim 1 wherein the internal form assembly is moved into anadjoining portion of the tunnel into which a tube section has beenpositioned so as to progressively form a continuous plastic linedtunnel.
 11. A ribbed plastic strip for forming spiral wound tubingcomprising complementary edge formations which engage to form the spiralwound tube and each edge formation having an projection adapted forinterlocking engagement with surrounding grout so as to hold the tubesection in position against external pressure such as ground waterpressure.
 12. A ribbed plastic strip according to claim 11 wherein theedge formations engage so as to form an external groove between thejoined edge formations into which bonding material may be placed to bondthe strips together.
 13. A method of forming a mandrel formed spiralwound pipe, comprising: spiral winding plastic strip onto a mandrel;joining together the adjacent edges of the strip to form a tube;ejecting a fluid from the mandrel beneath the formed tube to free theformed tube from the mandrel; and sliding the formed tube from themandrel.